KR100707415B1 - Electronic ballast for DC voltage with low input voltage and low input / output current protection circuit - Google Patents

Abstract

The present invention relates to an electronic ballast for direct current voltage having a low input voltage and a low input / output current protection circuit, and has a variety of control functions to develop a current detection circuit that detects an overload, miswiring or no-load condition due to a lamp failure. In order to achieve the object as described above, the electronic ballast for the DC voltage according to the present invention drives the lamp 8 by receiving a DC voltage and generating a high frequency output to control the ballast. Circuit section 5; A resonant circuit portion 6 constituting the resonant circuit with the lamp 8 by the high frequency output of the inverter circuit portion 5; A current sensing unit 7 for sensing an inverter current of the inverter circuit unit 5 corresponding to the lamp output current; A low voltage and low current comparison unit (2) for comparing a comparison voltage (V5) corresponding to the input voltage (V +) or the output value (I1) of the inverter current with a reference voltage (V6); And a control unit (3) in response to the output of the low voltage and low current comparison unit (2) for generating a control signal to stop the operation of the inverter unit to stop the operation of the ballast to protect the circuit; It includes.

Ballast, DC, Low Voltage, Low Current, Protection Circuit, Low Voltage Comparator

Description

ELECTRONIC BALLAST DRIVEN BY DC POWER SUPPLY HAVING THE CIRCUIT PROTECTED FROM LOW INPUT VOLTAGE AND LOW INPUT / OUTPUT CURRENT}

1 is a block diagram of an electronic ballast according to the present invention.

2 is a detailed circuit diagram of the electronic ballast according to the present invention.

3 is an operational characteristic diagram of a low voltage and low current comparator circuit of the present invention.

4 is an operation characteristic diagram of a high voltage and high current comparator circuit related to the present invention;

5 is an operation characteristic diagram of a control unit circuit of the present invention.

6 is an operation characteristic diagram of the inverter current detector circuit of the present invention.

7 is an operation characteristic diagram of a low voltage start circuit according to the present invention;

<Description of the symbols for the main parts of the drawings>

1. High voltage and high current comparator 2. Low voltage and low current comparator

3. Control part 4. Initial start circuit part

5. Inverter circuit section 6. Resonant circuit section

7. Current sensing unit 8. Lamp

The present invention relates to an electronic ballast for a direct current voltage having a low input voltage and a low input / output current protection circuit. When the input voltage is excessively lower than the set voltage with all control functions, Compare input voltage and control ballast with its comparative output.

In addition, when a low current occurs at the set value (for example, ± 20%) of the fluorescent lamp or inverter current at a normal input voltage, the operation of the electronic ballast is controlled by the control voltage of the current sensing unit. If one of the connecting wires is in contact with the luminaire or the ballast is installed without a load, the control voltage of the current sensing unit stops the ballast.

Electronic ballasts contain a starting semiconductor element in the ballast, which preheats the electrode with its switching action or electrode heating winding and starts the lamp by the semiconductor switching action, while the lamp is heated by the lamp current and the electrode heating winding during lighting. It is a ballast used for the circuit method

In general, the ballast for fluorescent lamps for D.C. has been mainly used for low power because it uses an inverter using a transistor. In addition, it has the advantage that it can operate at low voltage, but the base voltage of transistor is low (0.7V), so it cannot be equipped with the control function according to the situation of the ballast. , Had many disadvantages.

Therefore, the present invention improves the efficiency, which is a disadvantage of the conventional DC fluorescent ballast for solving the above problems, is suitable for high power, and equipped with various control functions, due to overvoltage input or defective lamp By developing a current detector circuit that detects an overload, incorrect wiring or no-load condition, the ballast is controlled to minimize the failure of the ballast. In particular, a circuit is added to improve the start of the inverter circuit so that it can operate even at low voltage.

In addition, while preventing overcurrent and overvoltage, the lamp current is limited within a predetermined range, thereby extending the life of the lamp.

The present invention protects the circuit by stopping the operation of the ballast when the polarity of the D.C voltage is changed and input.

Further objects and effects of the present invention will become more apparent from the following detailed description of the invention described with reference to the accompanying drawings.

In order to achieve the above object, the electronic ballast for DC voltage having a low input voltage and a low input output current protection circuit according to the present invention, the inverter for driving the lamp 8 by receiving a DC voltage to generate a high frequency output Circuit section 5; A resonant circuit portion 6 constituting the resonant circuit with the lamp 8 by the high frequency output of the inverter circuit portion 5; A current sensing unit 7 for sensing an inverter current of the inverter circuit unit 5 corresponding to the lamp output current; A low voltage and low current comparison unit (2) for comparing a comparison voltage (V5) corresponding to the input voltage (V +) or the output value (I1) of the inverter current with a reference voltage (V6); And a control unit (3) in response to the output of the low voltage and low current comparison unit (2) for generating a control signal to stop the operation of the inverter unit to stop the operation of the ballast to protect the circuit; It includes.

Preferably, the low voltage and low current comparator 2 includes a low voltage comparator U1A, and the input voltage of the comparator voltage V5 of the low voltage comparator U1A is a voltage divider resistor of the input voltage V +. The connection point of R4 and R5 is connected and the output terminal of the current sensing unit 7 connected to the connection point of the voltage dividing resistor is connected at the same time so that the divided voltage of the input voltage is applied to the comparison voltage input terminal. At the same time, the comparison voltage of the output current of the current sensing unit is applied, and the input voltage of the reference voltage V6 of the low voltage comparator U1A is connected to the connection point of the voltage divider resistor R7.R8 of the input voltage. The capacitor C3 connected in parallel with the one-side voltage divider R8 is connected to the connection point of the resistor, and the low voltage comparator (3) is formed by forming an integrated circuit formed by the other voltage divider resistor R7 and the capacitor C3. Comparison voltage input of U1A) A reference voltage input which becomes lower than the integrated voltage of the integrating circuit is reversed to the high output of the low-voltage comparator (U1A) at the low and characterized by stopping the operation of the ballast,

More preferably, the other voltage divider R7 may be implemented by using a negative temperature coefficient resistor (NTC) resistor, or the one voltage divider R8 may be implemented by using a positive temperature coefficient (PTC) resistor. It is possible to stop the operation of the ballast above the reference temperature by using the characteristic that the resistance value increases.

Preferably, the reverse current prevention diode D1 is connected to the DC input voltage input terminal, so that the ballast can be protected even if the polarity of the DC input voltage V + is changed.

As a result, the electronic ballast for the DC voltage according to the present invention compares a circuit for stopping the operation of the ballast when the polarity of the DC voltage is input and a high input voltage is applied to stop the operation of the ballast. High input voltage comparison circuit, Low input voltage comparison circuit that extends the life of secondary battery when low input voltage is applied, Over current occurs due to abnormality of lamp, wrong wiring or other situation In the current sensing unit circuit for detecting this and stopping the operation of the ballast, the low current comparison circuit and high current comparison circuit for comparing the sensed current of the current sensing unit, the control circuit for controlling the inverter unit, and the low voltage And a start circuit, a high frequency switching inverter unit, and a resonant circuit for improving the function of the inverter.

Best Mode for Carrying Out the Invention The preferred embodiment of the present invention will be described in detail according to the accompanying drawings.

1 is a block diagram of a D.C electronic fluorescent ballast of the present invention, Figure 2 is a detailed circuit diagram of the present invention, and will be described in detail accordingly.

First, the D.C input voltage is input through the diode D1. Therefore, when the polarity of the D.C voltage is changed, the operation of the ballast is stopped.

Now, the voltage input through the diode D1 (see (c) of FIG. 7) passes through the resistor R13 of the initial start circuit 4 and through the induction coil of the transformer T1, and the inverter unit 5. The inverter is initially started by applying a voltage to the gates of the FETs Q1 and Q2, which are the high frequency switching elements of the &quot;

By the start of the inverter section, the FETs Q1 and Q2 perform high frequency switching (see the first low sawtooth waveform in Fig. 7B).

On the other hand, high frequency switching of the FET of the inverter section induces a high high frequency voltage in the choke trans L1 (see the first high sawtooth waveform in Fig. 7B). The high frequency induction voltage of the choke transformer L1 passes through the capacitor C6 and the resistor R14 to maintain a constant voltage in the constant voltage circuit composed of the zener diode D10 and the capacitor C4 (see FIG. 7A). ), The inverter unit 5 is stably driven.

The high-speed switching voltage of the inverter unit 5 forms a square wave in the transformer T1 and the condenser C5, which are the resonant circuits 6, and applies a high frequency voltage to the filament through the condenser C7, thereby providing a lamp 8. Drive.

On the other hand, the switching current of the inverter unit 5 flows through the transformer T2 of the current sensing unit 7. The transformer T2 senses the inverter current I1 and forms a detection voltage Vo at the resistor R15, the diode D11, and the capacitor C3.

The detection voltage Vo formed by the inverter current sensing unit 7 passes through the resistor R9 and the diode D4 to the positive input of the comparator U1B of the high voltage and high current comparison circuit 1. V3). In addition, the breather voltage V4 by the voltage divider R2 and R3 of the input voltage V + is simultaneously applied to the (+) input terminal of the comparator U1B.

The negative input of the comparator U1B is applied by forming a constant reference voltage V2 by the resistor R1 and the zener diode D5.

The comparator U1B receives a control voltage V3 proportional to the breather voltage V4 by the voltage divider resistors R2 and R3 of the input voltage V + or the detection voltage Vo of the current sensing unit 7. Compare with the reference voltage (V2).

The operation of the electronic ballast for DC voltage having the low input voltage and the low input / output current protection circuit of the present invention will be described below with reference to FIGS. 3 to 7.

3 is an operation characteristic diagram of the low voltage and low current comparator circuit of the present invention, FIG. 4 is an operation characteristic diagram of the high voltage and high current comparator circuit related to the present invention, FIG. 5 is an operation characteristic diagram of the control circuit of the present invention, 6 is an operation characteristic diagram of an inverter current detector circuit according to the present invention, Figure 7 is an operation characteristic diagram of a low voltage start circuit according to the present invention.

First, if a miswiring or overload of the lamp occurs during the operation of the inverter unit 5, the current sensing unit 7 detects a current and (+) input of the high voltage comparator U1B of the high voltage and high current comparator 1 Raise the voltage V3.

As soon as the control voltage (V3: + input of U1B +) is higher than the reference voltage (V2:-input of U1B), the comparator U1B inverts the output V1 from low to high, and then When applied to the control unit 3 of the stage, the transistor Q3 is operated via the resistor R10 via the diode D3. Accordingly, by turning on the transistor Q3, the oscillation voltage of the inverter unit 5 is shorted through the diodes D6 and D7 to short the gate voltages of the FETs Q1 and Q2, which are switching elements, to stop the operation of the inverter unit. .

In addition, even when a high input voltage is applied, the voltage V4 divided by the voltage dividing resistors R2 and R3 causes the high voltage comparator U1B to provide a positive input voltage of the high voltage comparator U1B. Since the output of the comparator is raised to high, the transistor Q3 of the control unit is eventually operated to stop the operation of the inverter unit 5 similarly to the case where the control voltage is a high voltage.

On the other hand, if the power is applied at the time of poor connection of the lamp 8 and no load during operation, the worker is in danger of high frequency voltage.

A complementary circuit is the no-load and low current comparison circuit (2). Also referred to as the low voltage and low current comparator 2.

The low current comparison circuit 2 is composed of resistors R4, R5, R7 and R8, a capacitor C2 and a low voltage comparator U1A.

First, when the initial power is applied, the input voltage V + is breathed by the divided resistors R4 and R5, and the divided voltage V5 is applied as the negative input voltage of the low voltage comparator. On the other hand, as will be described later, the output terminal of the current detector 7 of the inverter current I1 is simultaneously connected to the negative input terminal of the low voltage comparator, and a signal corresponding to the output current of the ballast is detected and compared. Therefore, at the negative input terminal of the low voltage comparator, the low input voltage, the low input current and the low output current signal are all compared.

The positive input voltage of the low voltage comparator forms a reference voltage V6 at the divided resistors R7 and R8 and the capacitor C2. The positive input voltage V6 is gradually increased by an integrating circuit composed of a resistor R7 and a capacitor C2, and the charging voltage of the capacitor C2 is equal to the breather voltage of the resistors R7 and R8. Ascend and stop.

At this time, the negative input of the low voltage comparator U1A should be set slightly larger than the charging voltage of the capacitor C2 from the initial start than the positive input.

Now, when the operation of the low voltage and low current comparison unit 2 is described, when the connection failure and no load of the lamp 8 occur, the inverter current detection unit 7 generates a current I1 that is significantly lower than the normal current. It is detected by the detection voltage Vo.

The low detection voltage Vo of the current sensing unit 7 becomes the negative comparison input voltage V5 of the low voltage comparator U1A through the resistor R6, and thus the positive input voltage V6 which is a reference voltage. Since the lower voltage comparator U1A inverts the output V7 of the comparator 2 from low to high, the transistor of the controller 3 is passed through the diode D2 and the resistor R10. Since Q3 is operated, the transistor Q3 is turned on, so that the operation of the inverter section 5 is eventually stopped.

3 is an operation characteristic diagram of a low current circuit part, (a) is a negative input voltage (V5) of pin 5 of the low voltage comparator (U1A), (b) is a pin 6 of the comparator (+) Input (V6), and (d) indicates the output voltage (V7) of pin 7, and (c) indicates whether the entire ballast circuit is operating.

As shown in the figure, in the state where the power is ON and in normal operation, the negative input V5 of the low voltage comparator U1A always maintains a higher voltage than the positive input V6.

However, when the current sensing unit 7 detects a low current I1, as shown in the right side of FIG. 3, the negative input voltage V5 is lowered, and the reference voltage (+) At the moment lower than the input voltage V6, the low voltage comparator U1A outputs a high voltage V7, which eventually stops the operation of the ballast.

In addition, in the case of the low input voltage and the low input current, the negative input voltage V5 caused by the breather of the resistors R4 and R5 is lowered, so that the output V7 of the low voltage comparator U1A is made low ( Inverting from Low to High will stop the operation of the inverter unit 5.

On the other hand, the low voltage and low current comparison unit 2 of the present invention allows the configuration of a circuit to stop the operation of the ballast at a high temperature.

In the circuit of FIG. 2, the resistor R7 is implemented by using a negative temperature coefficient resistor (NTC) resistor to stop the operation of the ballast above a reference temperature by using a characteristic in which the resistance value falls at a high temperature. It is possible.

That is, when the resistor R7 is implemented using N.T.C, when the ambient temperature is high or heat is generated in the ballast, the N.T.C resistance of the resistor R7 is lowered.

When the NTC value of the resistor R7 decreases, the voltage V6 of the connection point of the resistor R8 and the capacitor C3 increases, and the low voltage comparator U1A inverts the output from low to high. By operating the control unit 3, it is possible to stop the operation of the ballast when the ambient temperature becomes high or when high heat generation occurs in the ballast.

Conversely, even when the resistor R8 is implemented using a positive temperature coefficient (P.T.C) resistor, the P.T.C resistance of the resistor R8 becomes large when the ambient temperature increases or a high heat generation occurs in the ballast.

Therefore, when the PTC value of the resistor R8 increases, the voltage V6 between the resistor R8 and the capacitor C3 connection point increases, and the low voltage comparator U1A inverts the output from low to high. By operating the control unit 3, it is possible to stop the operation of the ballast when the ambient temperature becomes high or when high heat generation occurs in the ballast.

4 is an operation characteristic diagram of the high voltage and high current comparator circuit 1, (a) shows the negative input voltage V3 of pin 3 of the high voltage comparator U1B, b) shows the positive input (V2) of pin 2 of the comparator, and (d) shows the output voltage (V1) of pin 1, and (c) shows whether the entire ballast circuit operates.

As shown in the figure, the high voltage comparator U1B controls the operation of the ballast by simultaneously comparing the high voltage of the input voltage V + and the high current of the inverter unit.

When the input voltage (V +) is higher than the preset setting voltage, the voltage (V3) of the (+) input (pin 3) of the high voltage comparator (U1B) is higher than the (-) input (pin 2) voltage (V2) that is the reference voltage. Therefore, the high voltage comparator inverts its output to high and operates the transistor Q3 of the control section 3, thereby stopping the operation of the inverter section 5 eventually.

In addition, even when overcurrent occurs in the inverter, the current detection unit 7 forms a high control voltage. That is, the high control voltage of the current sensing unit 7 is the voltage V3 of the (+) input terminal pin 3 of the high voltage comparator U1B and the voltage V2 of the (−) input terminal pin 2 which is a reference voltage. By making it higher than), the high voltage comparator U1B inverts the output V1 from low to high to operate the transistor Q3 of the control unit 3, resulting in the operation of the inverter unit 5. To stop.

Here, when the operation of the inverter unit 5 is stopped. The sensing voltage of the current sensing unit 7 is lowered. At this time, the operation of the ballast is stopped by the operation of the low voltage and low current comparing unit 2 circuit.

5 is an operation characteristic diagram of the transistor Q3 of the control unit 3 according to the output signals of the low and high voltage comparators U1A and U1B, (a) is a characteristic diagram of the output V7 of the low voltage comparator, b) is the output V1 characteristic diagram of the high voltage comparator, (d) shows the operating characteristic of the transistor Q3 of the control part 3, and (c) shows the operating characteristic of the inverter part 5.

When the input voltage V + and the inverter current IOU become higher than the specified voltage and current, the output V1 of the high voltage comparator U1B becomes high to operate the transistor Q3 of the controller 3. , Stop the inverter.

Even when the input voltage V + is lower than the specified value, the inverter driving current is also lowered, and the inverter driving current is low or almost no current flows even in the case of no load or a bad lamp connection.

In such a case, the output V7 of the low voltage comparator U1A becomes high to stop the operation of the inverter.

6 is an operation characteristic diagram of the circuit of the current sensing unit 7 of the present invention, where (a) is the current of the lamp 8 and (b) is the current I1 sensed by the current sensing unit 7. to be.

When a current that is considerably higher than the set current (for example, about + 20% or more) is generated in the inverter current sensing unit 7, the operation of the inverter 7 is stopped, and such an operation is performed three to four times.

With three to four ON / OFF operations of the inverter section, the inverter current sensing is sensed significantly lower than the set current (for example, below about -20%).

On the other hand, when a current that is significantly lower than the set current (for example, about −20% or less) is generated in the inverter current sensing unit 7, the inverter unit 5 operates as the output V7 of the low voltage comparator U1A. Will stop.

Finally, FIG. 7 is an operation characteristic diagram of the low voltage start circuit, in which (a) shows inverter driving characteristics, (b) shows characteristics of the choke transformer L1, and (c) shows voltage characteristics. Indicates an on / off state.

If the input voltage V + is smaller than the drive voltage 4.5V of the FETs Q1 and Q2, it is difficult to operate the inverter normally. In this case, the high induced voltage of the choke trans is formed by the operation of the inverter 5 to form a capacitor C6 and a resistor R14 circuit as shown in FIG. Increasing the gate voltage of the inverter operates stably.

Although the present invention has been described above with reference to the embodiments shown in the accompanying drawings, the present invention is not limited thereto, and various modifications may be made within a range easily understood by those skilled in the art. Therefore, the limitation of the present invention should be limited only by the following claims.

As described above, according to the ballast according to the present invention, when the DC input voltage (V +) is a low voltage, the input or output current is a low current, or in the case of poor grounding, the operation of the ballast to stop the circuit It is possible to protect, and when the ambient temperature is high or high heat generation occurs in the ballast, it is possible to stop the ballast operation, and also to protect the circuit of the ballast even if the polarity of the DC power supply is changed. .

For example, the DC voltage driven ballast used in the present invention is particularly suitable for the instant start method, the minimum input voltage is 20VDC, the normal input voltage is 27.6VDC, the maximum input voltage is 30VDC, the lamp current is 200mA, operating temperature Can be enabled when the over-voltage protection range is -20 ° C to 55 ° C, the overvoltage protection range is 400VDC or more, the shutdown temperature range is 105 ° C or more, and the overload protection range is 240mA or more. In addition, in the absence of the lamp, the output voltage can be almost 0 V, and the output short circuit inverter current can be 95 mA or less.

Claims (6)

An inverter circuit unit 5 which receives a DC input voltage V + and generates a high frequency output to drive the lamp 8; A resonant circuit portion 6 constituting the resonant circuit with the lamp 8 by the high frequency output of the inverter circuit portion 5; And A current sensing unit 7 for sensing an inverter current I1 of the inverter circuit unit 5 corresponding to the lamp output current as a voltage value Vo of a detection resistor; An electronic ballast for DC voltage comprising: the ballast, The voltage value Vo of the detection resistor corresponding to the inverter current I1 sensed by the current sensing unit 7 and the comparison voltage V5 proportional to the input voltage V + and the input current are referenced to the reference voltage V6. A low voltage and low current comparison unit (2) for outputting a signal when the inverter current (I1) is low current or the input voltage (V +) is low voltage or the input current is low current; And A control unit (3) for generating a control signal for stopping the operation of the inverter unit (5) so as to protect the circuit by stopping the operation of the ballast in response to the output of the low voltage and low current comparison unit (2); Electronic ballast for DC voltage having a low input voltage and low input and output current protection circuit further comprising. The method of claim 1, The low voltage and low current comparator 2 includes a low voltage comparator (U1A), The input terminal of the comparison voltage V5 of the low voltage comparator U1A is connected to a connection point of the voltage divider resistors R4 and R5 of the input voltage V +, and is connected to a connection point of the voltage divider resistor. The output terminal of 7) is connected at the same time so that the divided voltage of the input voltage is applied to the comparison voltage input terminal and the comparison voltage of the output current of the current sensing unit is applied. The electronic ballast of claim 1, wherein when the comparison voltage input of the low voltage comparator (U1A) is lower than the reference voltage, the output of the low voltage comparator (U1A) is inverted from low to high to stop the operation of the ballast. The method of claim 2, The input terminal of the reference voltage V6 of the low voltage comparator U1A is connected to the connection point of the voltage divider resistor R7.R8 of the input voltage and is connected in parallel with the one-side voltage divider resistor R8 to the connection point of the voltage divider resistor. The condenser C3 to be connected is connected and comprised, and by making the integrating circuit by the said other side voltage divider R7 and the capacitor C3, When the comparison voltage input of the low voltage comparator U1A is lower than the integral voltage of the integrating circuit which is a reference voltage input, the output of the low voltage comparator U1A is inverted from low to high to stop the operation of the ballast. Electronic ballast for. The method of claim 3, wherein By implementing the other voltage dividing resistor (R7) using a negative temperature coefficient resistor (NTC) resistance, by using a characteristic that the resistance value falls at a high temperature, it is possible to stop the operation of the ballast above the reference temperature electronic ballast. The method of claim 3, wherein By implementing the one-side voltage divider (R8) using a positive temperature coefficient (PTC) resistor, the electronic ballast for DC voltage capable of stopping the operation of the ballast above the reference temperature by using a characteristic that the resistance value increases at a high temperature . The method according to claim 1 or 2, The reverse current prevention diode (D1) is connected to the DC input voltage input terminal, so that the ballast can be protected even if the polarity of the DC input voltage (V +) is applied.

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